Accumulating clinical and genetic data indicate that cancer metastasis might occur much earlier in the course of disease than previously thought, even before the primary tumour is clinically detectable.

Considering these data, in a Perspective article in Nature Reviews Cancer, Christoph Klein proposes a sea change in how we view metastatic spread, which has important implications for the treatment of patients with cancer.

The long-held model of metastasis states that tumour cells leave to form metastatic tumours when the primary tumour has grown large. This allows time for the tumour cells to evolve characteristics that enable them to invade and grow elsewhere in the body. Klein presents the controversial ‘parallel progression model’ which proposes that tumour cells spread to distant sites when the primary tumour is still small. After they have migrated, they then develop the traits required to survive and grow within the tissues that they have invaded.

Doctors inform their decisions based on the size and molecular traits of primary tumours and the presence of detectable metastases, so this model could incite a re-evaluation of how cancer is diagnosed and treated.

This article is one of seven articles addressing key questions in the biology of metastasis that comprise a Focus on Migration and metastasis in the April issue of Nature Reviews Cancer.


Article DOI: 10.1038/nrc2627